what are two groups who discovered america by crossing the atlantic before columbus? (not the vikings)

Polynesians  and Romans

Explanation:  

In 1492, Christopher Columbus discovered America that changed the world forever. It commonly understood that Vikings and Polynesians got there before him.

Ancient Polynesian were navigators who sailed as far as Hawaii, New Zealand, and Easter Island, which required them to cross an ocean in small boats.

The evidence of chicken bones in America led the first archaeological evidence for contact between Polynesians and the indigenous peoples of South America.

The evidence for ancient Roman in the Americas comes from the artifact known as the Tecaxic-Calixtlahuaca head. The head is a terracotta figure that resembles a similarity to the Roman origin.

the causes of the dust bowls were severe droughts,   lands became dry and hard, temperature was higher than usual, hot and dry conditions killed crops, high winds. because of those factors, the winds kicked up dry soil and created clouds of dust.